Friday, March 23, 2012

The Reddit Ranking Algorithm

Reddit harnesses the power of the recency logarithm in its ranking algorithm.

Reddit weighs the first ten upvotes equally to the next 90 upvotes.

Reddit values Recency above all else.

The logarithm in the Reddit algorithm favors early pick up. Getting 10 upvotes is no easy task. Getting the next 90 is as hard. It's the same math used to express the strength of earthquakes.

Reddit's bias/variance towards recency has a cost.

High frequency/low recency power users are prone to scream 'repost' on a four hour old article. Casual redditors, who are slowpokes, are more likely to be annoyed with power users, who cause high downvote pressure on older content. ("Why the hate? This New York Times article from last week is new to me!")

This forms a major cleavage between occasional visitors, infrequent contributors, serial readers, and moderators. In fact, the most frequent users are the people who are downvoting you on reddit.